Plastic cutting arrangement

ABSTRACT

An arrangement comprising essentially two stationary hot wire grids and a third lower moveable hot wire grid is disclosed for noiselessly cutting randomly sized plastic block or scraps into relatively smaller uniform cubically-shaped pieces. Details are also disclosed for mounting the hot wires on the various grids to generate different shapes in three separate dimensions during a continuous operation.

United States Patent Wilgus Aug. 20, 1974 [54] PLASTIC CUTTINGARRANGEMENT 2,216,604 10/1940 Schwimmer 83/l7l X [76] Inventor: James L.Wilgus, Reliable Plastics,

Inc., 35 Middaugh St., Somerville, primary M. Meister NJ. 08876 [22]Filed: July 3, 1973 [21] Appl. No.: 376,144 ABSTRACT An arrangementcomprising essentially two stationary [52] U.S. Cl 83/171, 83/356.l,83/3562, hot wire grids and a third lower w hot wire 83/4043 83/6511grid is disclosed for noiselessly cutting randomly sized [51] Int. ClB26d 7/10 plastic block Scraps i relativdy smaller uniform [58] held ofSearch 83/16, 171, 212-1, cubically-shaped pieces. Details are alsodisclosed for 83/3561 3563, 3571 651-1 mounting the hot wires on thevarious grids to generate different shapes in three separate dimensionsdur- [56] References C'ted ing a continuous operation.

UNITED STATES PATENTS 'Niebur, Jr 83/2121 9 Claims, 5 Drawing FiguresPLASTIC CUTTING ARRANGEMENT BACKGROUND OF THE INVENTION This inventionrelates to a plastic cutting arrangement for continuously cuttingsmaller plastic blocks or creating other shapes from randomly sized andshaped plastic material. More particularly this invention concerns arecycling process for forming useful plastic shapes from plastic wasteand scrap.

Various cutting devices have been devised in the prior art to formregularly sized (uniform) pieces of plastic from relatively larger, butuniform, sections of raw material. These devices use hot wire" cutterswhich are simply lengths of resistance wire stretched over a supportingframework and electrically heated. Depending upon the size of theplastic rectangular sections desired one or more of these wires are usedand spaced a uniform distance apart. Then, the resistance wire isconnected to a voltage source and heated to a sufficient temperature toslice the raw block as it comes into contact with it. A second set ofwires oriented transversely to the aforementioned wires and situatedbelow those cutters have also been used to recut the block therebycreating elongated rectangular blocks of plastic. Thus it may beappreciated that the majority of plastic cutters known in the prior artoperate on the premise that the raw material to be cut is substantiallyuniform in shape.

It has been a problem in the plastic industry to find an economical wayof disposing of scrap plastic, i.e., the discarded waste of a molding orfabricating processes. Although generally such scrap materialsarerelatively light it can assume enormous proportions of bulk. Attemptsto reduce this bulk by chemical processes have proven to be eitherunsuccessful, expensive or cause objectionable odors. Also presentlyused grandulators are extremely noisy, or, often grind plastic sectionsexcessively and create dust as well as useless powders.

In general, it is an object of the present invention to provide a singlecutter apparatus for cutting scrap plastic of random sizes into useablepacking material of substantially uniform dimensions.

Another object is to produce a plastic cutter arrangement which can becontinuously fed to produce the useable packing material.

Another object is to produce a plastic cutter with the versatility forcontinuously forming compound or complex surfaces upon plastic stock.

SUMMARY OF THE INVENTION These and otherobjects are achieved inaccordance with an illustrative embodiment of my invention comprising agravity-fed hot wire plastic cutter in which the cutting wires areinstalled on three separate frameworks. The frameworks are mounted oneon top of the other, each in a substantially horizontal plane and suchthat the wire grid of the adjacent framework is transverse. The bottomframework .is moveable and can, uniquely, be used in accordance with myinvention to severe descending plastic sections after they have beenshaped by the first two wire girds, or to introduce compound surfaces onthe descending sections.

The resistance wire of the tow upper grids as well as the appliedvoltage thereto is choses on the basis of the speed of the continousoperation desired. To operate my cutter, the raw/scrap plastic is laidon the uppermost grid, cut by heat and dropped on to the next grid. Atthe middle grid it is cut in the tranverse direction and dropped to themoveable bottom grid.

The resistivity of the wire, and the voltage applied, determine thetemperature of the wires. The tempera ture of the first two sets of wiregrids, the stationary units, will effect the rate of descent of the cutplastic sections. The temperature of the bottom grid wiring and thespeed of the reciprocating motion of the bottom framework will determinethe length/shape of the finished product. For packaging material l havefound that a complete and quick separation of the decending rods occurrswith a wiretemperature of 800 F.

In addition to the foregoing l have illustrated herein various ways inwhich the distance separating the wires of a particular grid can bequickly and efficiently adjusted to meet different cutting requirements.Also, I envision the possibility that such adjustments can bedynamically performed during the shaping and cutting process tointroduces intricate shapes in the finished product as will be explainedhereinafter.

The foregoing as well as-other objects and features of my invention willbe appreciated from a consideratio of the attached drawing in which,

1 FIG. 1 describes in a projected view my illustrative plastic cutterassembly;

FIG. 2 shows details of a limit switch and its mounting; and

FIGS. 3 to 5 depict various alternative mounting schemes for the wiresof a grid to teach various types of apparatus for varying the spacingsof hot wires on a framework.

DETAILED DESCRIPTION spacing between these frameworks is ordinarilyuniform and that my invention in principle is not to be limited by thespacing arrangement of frameworks in FIG. 1

Frameworks l0, l1 and 12 have uniformly spaced resistance wires strungin a substantially horizontal plane for their entire lengths. In thefollowing discussion we will consider only the mechanical arrangement offramework 10 wiring but, as one can observe, much of this discussionalso applies to frameworks 1 1 and 12. Framework 10 has illustratively22 uniform spaced wires,-e.g. wire 20, strung between members 13 and 14.The ends of each wire, e.g. wire 20, are connected to tensioning springse.g. springs 15 and 16, to maintain proper alignment of each wire and toabsorb elongations due to temperature increase.

Each of the wires of frameworklO are connected to power supply 17 viacable 22 which as shown in FIG. 1 has three branch feeding cablesections 23-25 connected to all three frameworks. The return potentialof supply 17 is connected via cable 26 to the two upper frameowrks 10and 11 (not shown). The importance of separate cable 27 which connectspower supply 17 to framework 12 will be considered subsequently. Each ofthe wires of upper framework 10 are wired in parallel to cables 22 and26 and therefore are uniformly the same temperature. This is also trueof framework 11 because cables 22 and-26 feed the wires of that gridwiring in parallel with the wiring of framework 10.

Dependent upon the voltage potential difference and the resistivityfactor of the grid wiring, each wire is heated to a precise temperature.It is necessary to achieve a temperature of 800 F for satisfactoryoperation in most instances To a degree, faster operation may beachieved by a ,hotter wire grid but the useful life of the wiring mayalso be lessened. The gauge of wire, the resistivity of each wire andthe applied voltage are factors which must be determined for everyinstallation and are deemed to be within the skill of the art.

It is possible to eliminate the need for a transformer by threading acontinuous wire back and forth to form a grid of one physical andcontinuous wire. The current would remain the same for one wire whetherit be 30 inches or 30 feet. This could be referred to as a series grid,as opposed to a parallel grid, electrically speaking.

An important aspect of my invention-is the third grid on framework 12.This framework is continuously oscillating in the direction shown by thearrow heads of FIG. 1. Oscillator motor 30 is secured to member 31 andhas a thrust rod 32 connected to side edge 33 of framework 12. Motor 30is operated in conjunction with signals received from limit switches 40and 43 (switch 40 best seen in FIG. 2) which periodically reverse thewinding motor potentials to cause a thrustwithdrawal action of rod 32.

Framework 12 is wired similar to the upper frameworks but it connectsvia separate cable 24 to power supply 17. Thus the voltage potential ofthe moveable grid may be separately adjusted.

Framework 12 is equipped with the four flanged wheels, eg 34 and 35. Thewheels in the foreground of FIG. 1 are blocked from view by theframework surfaces and member 33 has been broken away to permit wheel34to be viewed. Each wheel, e.g. wheel 34, is constructed of twocontiguous concentric bodieseach of different diameters. The largerdiameter body 41 contacts and bears at its perphifery upon a lowerframework member, e.g. member 36. Thus, the sideway movement of moveableframework is constrained by the larger diameter surfaces of each wheel.

With reference to FIG. 2, the motion of framework 12 in response tomotor 30 is under control of a pair of limit switches 40 and 43 whichare activated by the motion of framework 12. These switches mayillustratively be pnuematic or electric, but the operational logic is'the same. As the framework moves toward'the front (see arrow), stop 45contacts toggle member 46 of switch 40. Stop 45 moves toggle member 46toward its rear position which causes the motor winding field toreverse. Framework 12' then moves rearward and a similar engagementoccurs with limit switch 43 (not shown in detail) to reverse the motorwinding again. Altemamelting process, it is possible to pass theproductsthrough a set of pinch rollers to break the surfaces. Inaddition, in some applications it may be desireable to pass the productsthrough a de-staticzing area to remove any electric charges.

WIRE GRID SECURING ARRANGEMENTS I have recognized that one potentialdrawback to the efficient and satisfactory general usuage of all plasticcutter apparatus is in the adjustment of the spacing of wires in a grid.In FIG. 1, Ive shown a relatively inflexible arrangement for maintainingthe spatial separation between wires. So long as no adjustments have tobe made, this arrangement is quite satisfactory. But, I visualize a moreadaptable system and to this end FIGS. 3 to 5 depict adjustable wirefastening arrangements.

FIG. 3 incorporates a threaded shaft 50 which to the left side ofmid-section 56 has a left-hand thread and to the right side has a righthand thread. Internally threaded nuts 52 and 53 engage respectively theleft and right hand sections of shaft 50 so that rotation thereof in onedirection moves the hot wires closer together and the opposite directionmoves them apart. Springs 54 and 55 maintain the tension of the hotwires as the adjustments are made.

FIG. 4 shows a cyclindrical member 61 about which a rather looselycoiled spring 60 is wrapped. At equal intervals, e.g. 62 and 63, alongspring 60 several hot wires are fastened via springs, e.g. 64 and 65. Asends 66 and 67 of spring 60 are placed under tension, or that tension isrelaxed, spacing d increases or decreases, respectively. This spacing isat all times equal between each of the hot wires and the spatialseparation is quite easily adjusted when tension in springs 64,65, etcis re laxed.

FIG. 5 shows a more theoretical approach to the general problem. Asshown an array of springs properly anchored, such as at points 71-74,can be arranged so that the hot wires are moved relative to anduniformly away from one another. As shown the stationary hot wire iswire 75 and as tension is applied or relaxed on ends 76 and 77 thedistance d relative to wire 75 changes. Note that this spaticaladjustments is uniform to either side of wire 75.

CONCLUSION It is considered to be within the skill of the art to makeminor variations in my teaching but such variations are also consideredto be within the spirit and scope of my invention. For example, it ispossible to have two synchoronously moving grids, or an aperiodic movinggrid to create intricate shapes in plastic. It is further possible toplace each of the grids under control of a device, such as a computer orother programned controls so that their relative positions as well aswire separations may be atuned to the material introduced at the top ofthe cutter.

What I claim is:

l. A gravity-fed cutter arrangement for shaping thermo-plastic materialcomprising a first framework having a plurality of equally spaced wires,said framework being secured to supporting members which position saidwires in a substantially horizontal plane, a second framework alsosecured to said supporting members and aligned below said firstframework, said second framework having a second purality of equallyspaced wires lying substantially in a horizontal plane and orientedtranverse to said first plurality of wires, and a third frameworkaligned below said second framework and having a third plurality of ofequally spaced wires, said third framework being adapted forreciprocating motion within a horizontal plane under said aligned firstand second frameworks.

2. The invention set forth in claim 1 further including means forconnecting a source of voltage potential to all of said wires in thefirst, second and third frameworks concurrently.

3. The invention set forth in claim 1 further including a first andsecond voltage potential, said first voltage potential being connectedto said first and second plurality of wires, and said second voltagepotential being connected to said third plurality of wires whereby adifferent voltage potential is connected to the wires of the frameworksubjected to reciprocal motion.

4. The invention set forth in claim 1 wherein at least one of saidframeworks contains means for automatically and uniformly adjusting thespatial separation between the wires therein. a

5. The invention set forth in claim 1 further including guiding means onsaid supporting members and cooperating guiding means on said thirdframework for constraining the reciprocating motion of said thirdframework in alignment under said first and second frameworks.

6. The invention set forth in claim 1 wherein said wiring in each ofsaid frameworks is series wired and thereby adapted to carry a uniformelectric current there through.

7. A gravityfeed plastic cutter apparatus for slicing thermo-plasticmaterial along three separate axes, said apparatus comprising a firstrectangular framework secured to an upright supporting member forpositioning said framework in a horizontal plane, said frameworkincluding a first plurality of evenly spaced wires attached to oppositesides of said framework, a second rectangular framework also secured tosaid supporting member so as to be aligned directly below said firstframework is a plane parallel thereto, said second framework including asecond plurality of evenly spaced wires attached to opposite sides ofsaid second framework and oriented tranverse to said first plurality ofwires, a third rectangular framework moveable mounted in said supportingmember below said second framework and including therein a thirdplurality of evenly spaced wires attached to opposite sides of saidthird framework, means connecting said third framework to saidsupporting member for restricted reciprocating motion within ahorizontal plane and along an axes parallel to said second plurality ofwires, said third plurality of wires being oriented transverse to saidsecond plurality of wires, and means for coupling a voltage potential tothe wires of all said frameworks to activate the thermo-plastic cuttingprocess.

8. The invention of claim 7 further including means for uniformlyadjusting the relative spatial separation of wires in at least one ofsaid framework.

9. The invention of claim 7 wherein the voltage potential applied tosaid wires causes the generation of wire temperatures in the order of800 F.

1. A gravity-fed cutter arrangement for shaping thermo-plastic materialcomprising a first framework having a plurality of equally spaced wires,said framework being secured to supporting members which position saidwires in a substantially horizontal plane, a second framework alsosecured to said supporting members and aligned below said firstframework, said second framework having a second purality of equallyspaced wires lying substantially in a horizontal plane and orientedtranverse to said first plurality of wires, and a third frameworkaligned below said second framework and having a third plurality of ofequally spaced wires, said third framework being adapted forreciprocating motion within a horizontal plane under said aligned firstand second frameworks.
 2. The invention set forth in claim 1 furtherincluding means for connecting a source of voltage potential to all ofsaid wires in the first, second and third frameworks concurrently. 3.The invention set forth in claim 1 further including a first and secondvoltage potential, said first voltage potential being connected to saidfirst and second plurality of wires, and said second voltage potentialbeing connected to said third plurality of wires whereby a differentvoltage potential is connected to the wires of the framework subjectedto reciprocal motion.
 4. The invention set forth in claim 1 wherein atleast one of said frameworks contains means for automatically anduniformly adjusting the spatial separation between the wires therein. 5.The invention set forth in claim 1 further including guiding means onsaid supporting members and cooperating guiding means on said thirdframework for constraining the reciprocating motion of said thirdframework in alignment under said first and second frameworks.
 6. Theinvention set forth in claim 1 wherein said wiring in each of saidframeworks is series wired and thereby adapted to carry a uniformelectric current there through.
 7. A gravity-feed plastic cutterapparatus for slicing thermo-plastic material along three separate axes,said apparatus comprising a first rectangular framework secured to anupright supporting member for positioning said framework in a horizontalplane, said framework including a first plurality of evenly spacEd wiresattached to opposite sides of said framework, a second rectangularframework also secured to said supporting member so as to be aligneddirectly below said first framework is a plane parallel thereto, saidsecond framework including a second plurality of evenly spaced wiresattached to opposite sides of said second framework and orientedtranverse to said first plurality of wires, a third rectangularframework moveable mounted in said supporting member below said secondframework and including therein a third plurality of evenly spaced wiresattached to opposite sides of said third framework, means connectingsaid third framework to said supporting member for restrictedreciprocating motion within a horizontal plane and along an axesparallel to said second plurality of wires, said third plurality ofwires being oriented transverse to said second plurality of wires, andmeans for coupling a voltage potential to the wires of all saidframeworks to activate the thermo-plastic cutting process.
 8. Theinvention of claim 7 further including means for uniformly adjusting therelative spatial separation of wires in at least one of said framework.9. The invention of claim 7 wherein the voltage potential applied tosaid wires causes the generation of wire temperatures in the order of800* F.